Messages in this thread | | | Date | Wed, 23 Oct 2013 00:26:16 -0500 | Subject | Re: lz4hc compression in UBIFS? | From | Brent Taylor <> |
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Konstantin, I did my testing with data from /dev/urandom (which I now realize wasn't the best choice of data source), but if I use /dev/zero (which actually causes data compression to occur), the decompressor fails. I don't know the internal workings of the lz4hc compressor or the lz4 decompressor. I couldn't find any examples of any code in the kernel actually using the compressor. I've cc'ed the maintainers of the lz4hc_compress.c to see if they my have some more insight to the issue.
-- Brent
On Tue, Oct 22, 2013 at 5:10 AM, Konstantin Tokarev <annulen@yandex.ru> wrote: > > > 22.10.2013, 07:43, "Brent Taylor" <motobud@gmail.com>: >> On Mon, Oct 21, 2013 at 10:59 AM, Konstantin Tokarev <annulen@yandex.ru> wrote: >> >>> 04.10.2013, 07:09, "Brent Taylor" <motobud@gmail.com>: >>>> Here is a patch based on linux-3.12-rc3. I haven't performed any >>>> performance testing UBIFS using lz4hc, but I can mount UBIFS volumes >>>> and haven't seen any problems yet. The only think I know that isn't >>>> correct about the patch is the description for the Kconfig element for >>>> select lz4hc as a compression option. I only copied the description >>>> from the lzo description. >>> Hi Brent, >>> >>> I'm testing your patch on my SH4 device. When I create new partition >>> with lz4hc compressor, it works fine: I can copy file into it, and >>> md5sums of original and copy match. However, after reboot I cannot >>> read the file anymore: >>> >>> UBIFS error (pid 1101): ubifs_decompress: cannot decompress 934 bytes, compressor lz4hc, error -22 >>> UBIFS error (pid 1101): read_block: bad data node (block 1, inode 65) >>> UBIFS error (pid 1101): do_readpage: cannot read page 1 of inode 65, error -22 >>> >>> The same error appears if I use lz4hc-compressed ubifs image to flash rootfs >>> (using patched mkfs.ubifs). >>> >>> Decompression error occurs in lz4_uncompress() function (lib/lz4/lz4_decompress.c), >>> on the line 101: >>> >>> /* Error: offset create reference outside destination buffer */ >>> if (unlikely(ref < (BYTE *const) dest)) >>> goto _output_error; >>> >>> Brent: are you able to read data from lz4hc volume on your device? >>> Anyone: any ideas what may happen here? >>> >>> -- >>> Regards, >>> Konstantin >> >> Konstantin, >> I haven't seen anything like that on my at91sam9m10g45-ek >> development board. I haven't used a flash image from mkfs.ubifs yet. >> Is it possible the file system was not umounted cleanly before the >> reboot and UBIFS went through a recovery procedure? Maybe something >> breaks with lz4hc when UBIFS does a recovery? That's just a guess. > > Could you save attached file on lz4hc volume, umount it and mount again? > I get aforementioned error when doing `cat set11.cfg` > > -- > Regards, > Konstantin
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